What is 'semi- conservative' DNA replication ? Who discovered it and when?

Explanation

The replication where one of the two strands synthesized remains old and other becomes new is called semi-conservative replication. Matthew Messelson and Franklin Stahl (1958) proved experimentally that DNA Shows semi-conservative replication. They grew E. coli cells in a medium containing `N^15` and allowed to grow on a medium having `N^14`. The analysis were done after different number of generations. After first generation it showed that one of the two strands of newly synthesized DNA was radioactive `(N^15)` and other was non-radioactive `(N^14)`. After second generation it showed that in one DNA molecule one strand was radioactive and other was non-radioactive. Thus these experiments prove that DNA shows semi-conservative replication.